I. Field of the Invention
The present invention relates generally to the field of electrical fuses and, more particularly, to plug-in fuses with simplified methods to determine fuse condition.
II. Description of the Related Art
Electrical fuses provide reliable and economical protection for electrical wiring and components. Because of their small size and low cost, plug-in fuses have found wide use in industrial and consumer products such as automobiles, aircraft, air conditioning and heating equipment.
Due to the complexity of such applications, manufacturers often utilize fuse blocks or holders having multiple fuse receptacles. In order to minimize space requirements, fuse receptacles are densely packed, allowing minimal space for inspection, insertion and removal of the fuses. Component packaging often dictates placement of the fuse holders in inaccessible areas, increasing the problem of accessing individual fuses for troubleshooting, testing, and replacement.
In the past, inspection of a fuse to determine its condition required removal of the fuse and subsequent testing of the fuse with a meter such as a volt-ohm meter. The removal, testing and re-insertion of a fuse, especially if the fuse holder is in an inconvenient location, can become a tedious chore, increasing the time and cost for troubleshooting and repair of equipment. Close spacing of fuses often requires use of a tool to aid in the removal and/or insertion of the fuse. Such requirement for specialized tools and equipment prevents inexperienced users from performing an otherwise simple task.
Various fuse designs have been introduced to address the problem of inspecting the condition of a fuse, and to make the fuse easier to remove and re-install. U.S. Pat. No. 4,604,602 discloses a plug-in fuse with an overhanging upper portion to improve grasping of the fuse. U.S. Pat. No. 4,670,729 discloses a plug-in fuse with a transparent case to allow visual determination of the condition of the fuse link. U.S. Pat. No. 4,308,516 discloses a plug-in fuse with a high-resistance, heat responsive member which changes color upon heating. U.S. Pat. No. 5,598,138 discloses a fault-indicating blade fuse utilizing a LED or incandescent bulb which lights upon opening of the fuse element.
Despite a significant number of fuse designs introduced, there remains a significant need for improvement in fuse condition monitoring and fuse removal/insertion features.